1. Field of the Invention
This invention relates to an electric communication system, and more particularly to a data transmission system particularly suitable for use in the transfer of data between peripheral equipment and a computer or between two computers.
2. Description of Prior Art
In transferring data between two computers, it has been the usual practice to provide two lines between the computers for sending clock signals on one line and transferring data on the other line in terms of binary data signals of "1" and "0" which are expressed by the presence or absence of a pulse signal. The known data transmission systems of this nature are disadvantageous in that they require two transmission lines and use a unipoler pulse which necessitate use of a particular combination of a number of "1" and "0" pulses for forming a subsidiary signal such as a message start signal or the like, resulting in prohibitive complication of the circuit. On the other hand, the known asynchronous transmission systems which use a single line also require use of a complicated pulse waveform for the subsidiary signal and therefore of complicated circuit arrangement.